1. Field of the Invention
The present invention relates to a ceramic electronic part, such as a laminated capacitor, and a method for producing the same. More specifically, it relates to a ceramic electronic part with an improved shape for the lateral edges of its internal electrodes and a method for producing the same.
2. Description of the Related Art
FIG. 6 is a cross-sectional view showing an embodiment of a conventional laminated capacitor. The laminated capacitor 51 has a ceramic sintered compact 52 comprising dielectric ceramics. A plurality of internal electrodes 53a to 53d are formed in the ceramic sintered compact 52 such that they are superimposed in the thickness direction via respective ceramic layers. The internal electrodes 53a, 53c extend to the end face 52a, and the internal electrodes 53b, 53d extend to the end face 52b. External electrodes 54, 55 cover the end faces 52a, 52b, respectively.
The ceramic sintered compact 52 to be used in the above-mentioned laminated capacitor 51 is produced by the process described below. A plurality of ceramic green sheets having internal electrodes 53a to 53d printed thereon are laminated together with an optional number of unprinted ceramic green sheets located on the upper and lower surfaces of the compact so as to obtain a laminated product. A conductive paste is used to form the internal electrodes. After the laminated product has been pressed in the thickness direction, it is baked.
Because the internal electrodes 53a to 53d are formed by baking the printed conductive paste, they have a substantially homogeneous thickness. The tip (one lateral edge) of the internal electrode 53a, that is, the part shown in the circle in FIG. 6, is shown in an enlarged view of FIG. 7A.
As apparent from FIG. 7A, the internal electrode 53a has a substantially homogeneous thickness to the tip. As shown in FIG. 7B, in some cases the tip of the internal electrode 53a may have a slight roundness.
However, due to the above-mentioned shape of the internal electrode, when the ceramic sintered compact 52 is formed, peel-off among the ceramic layers or the phenomenon called delamination sometimes occurs. This can be attributed to the fact that when the laminated product is pressed prior to baking, portions where the internal electrodes exist are compressed strongly in the thickness direction so as to have a higher density, whereas portions where the internal electrodes do not exist are insufficiently compressed. As a result, the density of the portions B, C and D shown in FIG. 7A before baking vary in the order B&gt;D&gt;C. This variation causes delamination or inter-layer peel-off in the sintered compact. In particular, in the case of an internal electrode with a thickness of 3 .mu.m or more (used for high reliability), this phenomena has been remarkable.
A method for alleviating the reduction in density in the part shown as C in FIG. 7A is disclosed in Japanese Unexamined Patent Publication No. 8-58259. This publication proposes a method of printing a conductive paste, using a special screen printing plate, wherein the thickness of the internal electrode in the vicinity of its outer rim is thinner than at its other parts. The cross-sectional shape of an internal electrode formed according to this method is shown in FIG. 8. In the vicinity of the outer rim of the internal electrode 56 shown in FIG. 8, the internal electrode 56 is thinner at part 56b as a result of the presence of step 56a.
However, even in the sintered compact obtained by the method disclosed in the official gazette of Japanese Unexamined Patent Publication No. 8-58259, delamination and inter-layer peel-off is not satisfactorily prevented, and further improvement is desired.